One of the best airplanes ever realized by the European Aircraft industry was the Dornier Do 28D ... more One of the best airplanes ever realized by the European Aircraft industry was the Dornier Do 28D Skyservant, an extraordinary STOL light utility aircraft with the capability to carry up to 13 passengers. It has been a simple and rugged aircraft capable also of operating under arduous conditions and very easy and simple maintenance.
The architecture of this airplane, which has operated actively for more than 20 years, is very interesting analyzing the implementation of a new propulsion system because of the unusual incorporation of two engines, as well as the two main landing gear shock struts of the faired main landing gear attached to short pylons on either side of the forward fuselage. This unconventional design allows an easy implementation of different propulsion units, such as the history of different experimental versions allowed.
This paper presents the preliminary definition of an increased performance cogeneration system for optimizing the energy efficiency and maximizing the thrust of ducted fan propeller. It then produces an effective design of the ACHEON nozzle for such an aircraft, the definition of the optimal positioning for stability and efficiency. In conclusion, it analyses the expected performances of the resulting aircraft architecture.
Outstanding results allows verifying an effective possibility of implementing the ACHEON Coanda effect thrust and vector propulsion system on real aircraft.
The noise emitted by an electrical pump is mainly generated by different sources, (mechanic impac... more The noise emitted by an electrical pump is mainly generated by different sources, (mechanic impacts of rotor, fluid dynamic turbulences) but it is also affected by the structural response of each component of the pump. In this paper experimental results of the acoustic characterisation of an electrical pump is presented in order to point out the influence of different noise sources to the emitted noise power. Different techniques of investigations have been performed: measurements of the acoustic field are carried out and compared with vibration response of the pump. A parallel investigation of the thermograph radiation during the start up was also performed in order to a better understanding of the localisation on noise sources.
A finite difference technique is developed for evaluating the rate of heat transfer in the therma... more A finite difference technique is developed for evaluating the rate of heat transfer in the thermal entrance region of ducts with axial conduction. The pipe is assumed to extend from minus to plus infinity, while the velocity profile is fully developed. The boundary condition selected is a uniform heat flux for z greater than or equal to 0, while the wall temperature is kept uniform and equal to its minus infinity value for z less than 0. The results show that axial conduction and heat losses from the unheated section of the pipe significantly affect the temperature profile at the inlet of the heated part lower than the local mixed mean temperatures immediately downstream from the start of the heating. It is found that the performance of this type of heat exchanger can be described by a new parameter as an alternative to the usual Nusselt number.
ABSTRACT A cyclorotor (also known as a cyclocopter or cyclogiro) is a rotating-wing system where ... more ABSTRACT A cyclorotor (also known as a cyclocopter or cyclogiro) is a rotating-wing system where the span of the blades runs parallel to the axis of its rotation. The pitch angle of each of the blades is varied cyclically by mechanical means such that the blades experiences positive angles of attack at both the top and bottom positions of the azimuth cycle. The resulting time-varying lift and drag forces produced by each blade can be resolved into the vertical and horizontal directions. Varying the amplitude and phase of the cyclic blade pitch can be used to change the magnitude and direction of the net thrust vector produced by the cyclorotor. Compared to a conventional rotor, each spanwise blade element of a cyclorotor operates at similar aerodynamic conditions (i.e., at similar flow velocities, Reynolds numbers, and angles of incidence), and so the blades can be optimized to achieve the best aerodynamic efficiency. Moreover, because the blades are cyclically pitched once per revolution (1/rev), unsteady flow mechanisms may delay blade stall onset and in turn may augment the lift produced by the blades. Albeit proposed to MAV-scale, its use on large scale vehicles turns problematic, and we proposed in this paper to address their stopovers. Furthermore, since the thrust vector of a cyclorotor can be instantaneously set to any direction perpendicular to the rotational axis, a cyclorotor-based air vehicle may ultimately show better maneuverability and agility as compared to a classical powered conventional rotor system. One major drawback of a cyclorotor is its relatively large rotating structure which might offer a weight penalty when compared to a conventional rotor.
In the present paper, numerical investigations are carried out in a newly proposed propulsive sys... more In the present paper, numerical investigations are carried out in a newly proposed propulsive system Aerial Coanda high-efficiency orienting jet nozzle (ACHEON), which supports thrust vectoring and its application to prototype unmanned aerial vehicles (UAVs). The ACHEON system is presently being proposed for propelling a new vertical and short takeoff (V/STOL) airplane in the European Union. This system is powered by two axial electric turbofans and uses the Coanda effect (attachment of the jet to a curved surface) to achieve precise control of the thrust angle. The present study investigates the thrust vectoring efficiency of this newly patented nozzle and its integration with UAV aircraft. This study numerically investigates the 3D effects on this new machine and proposes remedies to solve the associated problems. Further, swirling effects generated by electric turbofans were studied in great detail. The effect of uniform and nonuniform velocity profiles were investigated on thrust vectoring efficiency of the nozzle. Then, the aerodynamic features of prototype UAVs were determined under various flow conditions. The interaction of the exit nozzle flow with incoming airstream was studied. Computational fluid dynamics (CF) calculations were carried out using Reynolds averaged Navier-Stokes (RANS) equations. A numerical method based on finite volume formulation (FVM) was used. Turbulent flow is modeled by using the SST k-ω model. Numerical results show that the presence of swirling velocities in the flow field significantly affects the thrust vectoring efficiency of the nozzle. From numerical simulations of the aircraft, it was found that the aerodynamic characteristics are strongly affected by the exit air jet angle.
Coanda effect is the adhesion of fluid on a convex surface. This paper presents the effect of tem... more Coanda effect is the adhesion of fluid on a convex surface. This paper presents the effect of temperature on the Coanda flow and shows how the temperature of the surface can influence the flow behaviour. It has been found that there are two mechanisms which influence the flow behaviour; both have contrary effect on the flow. One is based on variable Prandtl number and another is based on constant Prandtl number (thermal diffusivity) effect. The increment of the thermal diffusivity has prolonged separation of the boundary layer, while other mechanism triggers the earlier detachment of the flow from the curved surface. The preliminary CFD evaluation has provided the important controlling parameter for the thrust deflection.
The energy balance for an atmospheric layer near the soil is evaluated. By integrating it over th... more The energy balance for an atmospheric layer near the soil is evaluated. By integrating it over the whole day period, a linear relationship between the global daily solar radiation on a horizontal surface and the product of the sunshine hours at clear sky with the daily maximum temperature variation is achieved. The results for the monthly averaged daily values show a comparable accuracy with some well recognized models such as the Å ngströ m-Prescott one, at least for Mediterranean climatic area. Validation of the results has been performed using old data sets which are almost contemporary and relative to the same sites with the ones used for the comparison.
The energy balance for an atmospheric layer near the soil is evaluated. By integrating it over th... more The energy balance for an atmospheric layer near the soil is evaluated. By integrating it over the whole day period a linear relationship between the global daily solar radiation incident on a horizontal surface and the product of the sunshine hours at clear sky with the maximum temperature variation in the day is achieved. The results show a comparable accuracy with some well recognized solar energy models such as the Ångström-Prescott one, at least for Mediterranean climatic area. Validation of the result has been performed using old dataset which are almost contemporary and relative to the same sites with the ones used for comparison.
This paper compares hydrogen production by photovoltaic powered electrolysis of water at sea leve... more This paper compares hydrogen production by photovoltaic powered electrolysis of water at sea level and at low stratospheric altitudes up to 21 km. All the hydrogen production process has been considered from catchable solar radiation to storage technologies. The evaluation has been performed for 1 m 2 of flat horizontal plane. It has been considered the electric energy amount produced considering variations in equilibrium temperature and in solar. Hydrogen production through electrolysis has been evaluated too.
ABSTRACT This paper aims at defining a design methodology for the global thermodynamic performanc... more ABSTRACT This paper aims at defining a design methodology for the global thermodynamic performance of a high altitude airship cabin. This design method applies to different systems, which could not use the traditional air conditioning plant layout based on bleed air intake from the compressor stage of jet engines. In the case of electrically propelled green vehicles and airships, other energy sources must be exploited. The MAAT EU FP7 project presents an innovative, energetically self sufficient, airship system based on cruiser-feeder architecture. Both the cruiser and feeder are fed by photovoltaic energy. The energy storage system by electrolysis and fuel cells with intermediate energy storage by hydrogen and oxygen is characterized by high temperature energy dispersions (about 800-1000 °C for High temperature SOFC cells). This situation encourages the definition of a novel pressurization and air conditioning system. A preliminary cabin sizing with some structural considerations, an energetic evaluation of the thermal insulation of the cabin and a general balance of the energy production system are provided
Coanda effect (adhesion of jet flow over curved surface) is fundamental characteristics of jet fl... more Coanda effect (adhesion of jet flow over curved surface) is fundamental characteristics of jet flow. In the present paper, we carried out numerical simulations to investigate Coanda flow over a curved surface and its application in a newly proposed Propulsive system "A.C.H.E.O.N" (Aerial Coanda High Efficiency Orienting jet Nozzle) which supports thrust vectoring. The ACHEON system is presently being proposed for propelling a new V/STOL airplane in European Union. This system is based on cumulative effects of three physical effects such as (1) High speed jet mixing speeds (2) Coanda effect control by electrostatic fields (3) Coanda effect adhesion of an high speed jet to a convex surface. The performance of this nozzle can be enhanced by increasing the jet deflection angle of synthetic jet over the Coanda surface. This newly proposed nozzle has wide range of applications. It can be used in industrial sector such as plasma spray gun and for direct injection in combustion chamber to enhance the efficiency of the combustion chamber. Also, we studied the effect of Dielectric barrier discharge (DBD) plasma actuators on A.C.H.E.O.N system. Dielectric barrier discharge (DBD) plasma actuators are active control devices for controlling boundary layer and to delay the flow separation over any convex surfaces. Computations were performed under subsonic condition. Two dimensional CFD calculations were carried out using Reynolds averaged Navier stokes equations (RANS). A numerical method based on finite volume formulation (FVM) was used. SST k-ω model was considered to model turbulent flow inside nozzle. DBD model was used to model the plasma. Moreover, a body force treatment was devised to model the effect of plasma and its coupling with the fluid. This preliminary result shows that, the presence of plasma near Coanda surface accelerates the flow and delays the separation and enhances the efficiency of the nozzle.
ABSTRACT Export Date: 7 December 2013, Source: Scopus, References: Pedro, G., Suleman, A., Djilal... more ABSTRACT Export Date: 7 December 2013, Source: Scopus, References: Pedro, G., Suleman, A., Djilali, N., A numerical study of the propulsive efficiency of a flapping hydrofoil (2003) International Journal for Numerical Methods in Fluids, 42, pp. 493-526;
One of the best airplanes ever realized by the European Aircraft industry was the Dornier Do 28D ... more One of the best airplanes ever realized by the European Aircraft industry was the Dornier Do 28D Skyservant, an extraordinary STOL light utility aircraft with the capability to carry up to 13 passengers. It has been a simple and rugged aircraft capable also of operating under arduous conditions and very easy and simple maintenance.
The architecture of this airplane, which has operated actively for more than 20 years, is very interesting analyzing the implementation of a new propulsion system because of the unusual incorporation of two engines, as well as the two main landing gear shock struts of the faired main landing gear attached to short pylons on either side of the forward fuselage. This unconventional design allows an easy implementation of different propulsion units, such as the history of different experimental versions allowed.
This paper presents the preliminary definition of an increased performance cogeneration system for optimizing the energy efficiency and maximizing the thrust of ducted fan propeller. It then produces an effective design of the ACHEON nozzle for such an aircraft, the definition of the optimal positioning for stability and efficiency. In conclusion, it analyses the expected performances of the resulting aircraft architecture.
Outstanding results allows verifying an effective possibility of implementing the ACHEON Coanda effect thrust and vector propulsion system on real aircraft.
The noise emitted by an electrical pump is mainly generated by different sources, (mechanic impac... more The noise emitted by an electrical pump is mainly generated by different sources, (mechanic impacts of rotor, fluid dynamic turbulences) but it is also affected by the structural response of each component of the pump. In this paper experimental results of the acoustic characterisation of an electrical pump is presented in order to point out the influence of different noise sources to the emitted noise power. Different techniques of investigations have been performed: measurements of the acoustic field are carried out and compared with vibration response of the pump. A parallel investigation of the thermograph radiation during the start up was also performed in order to a better understanding of the localisation on noise sources.
A finite difference technique is developed for evaluating the rate of heat transfer in the therma... more A finite difference technique is developed for evaluating the rate of heat transfer in the thermal entrance region of ducts with axial conduction. The pipe is assumed to extend from minus to plus infinity, while the velocity profile is fully developed. The boundary condition selected is a uniform heat flux for z greater than or equal to 0, while the wall temperature is kept uniform and equal to its minus infinity value for z less than 0. The results show that axial conduction and heat losses from the unheated section of the pipe significantly affect the temperature profile at the inlet of the heated part lower than the local mixed mean temperatures immediately downstream from the start of the heating. It is found that the performance of this type of heat exchanger can be described by a new parameter as an alternative to the usual Nusselt number.
ABSTRACT A cyclorotor (also known as a cyclocopter or cyclogiro) is a rotating-wing system where ... more ABSTRACT A cyclorotor (also known as a cyclocopter or cyclogiro) is a rotating-wing system where the span of the blades runs parallel to the axis of its rotation. The pitch angle of each of the blades is varied cyclically by mechanical means such that the blades experiences positive angles of attack at both the top and bottom positions of the azimuth cycle. The resulting time-varying lift and drag forces produced by each blade can be resolved into the vertical and horizontal directions. Varying the amplitude and phase of the cyclic blade pitch can be used to change the magnitude and direction of the net thrust vector produced by the cyclorotor. Compared to a conventional rotor, each spanwise blade element of a cyclorotor operates at similar aerodynamic conditions (i.e., at similar flow velocities, Reynolds numbers, and angles of incidence), and so the blades can be optimized to achieve the best aerodynamic efficiency. Moreover, because the blades are cyclically pitched once per revolution (1/rev), unsteady flow mechanisms may delay blade stall onset and in turn may augment the lift produced by the blades. Albeit proposed to MAV-scale, its use on large scale vehicles turns problematic, and we proposed in this paper to address their stopovers. Furthermore, since the thrust vector of a cyclorotor can be instantaneously set to any direction perpendicular to the rotational axis, a cyclorotor-based air vehicle may ultimately show better maneuverability and agility as compared to a classical powered conventional rotor system. One major drawback of a cyclorotor is its relatively large rotating structure which might offer a weight penalty when compared to a conventional rotor.
In the present paper, numerical investigations are carried out in a newly proposed propulsive sys... more In the present paper, numerical investigations are carried out in a newly proposed propulsive system Aerial Coanda high-efficiency orienting jet nozzle (ACHEON), which supports thrust vectoring and its application to prototype unmanned aerial vehicles (UAVs). The ACHEON system is presently being proposed for propelling a new vertical and short takeoff (V/STOL) airplane in the European Union. This system is powered by two axial electric turbofans and uses the Coanda effect (attachment of the jet to a curved surface) to achieve precise control of the thrust angle. The present study investigates the thrust vectoring efficiency of this newly patented nozzle and its integration with UAV aircraft. This study numerically investigates the 3D effects on this new machine and proposes remedies to solve the associated problems. Further, swirling effects generated by electric turbofans were studied in great detail. The effect of uniform and nonuniform velocity profiles were investigated on thrust vectoring efficiency of the nozzle. Then, the aerodynamic features of prototype UAVs were determined under various flow conditions. The interaction of the exit nozzle flow with incoming airstream was studied. Computational fluid dynamics (CF) calculations were carried out using Reynolds averaged Navier-Stokes (RANS) equations. A numerical method based on finite volume formulation (FVM) was used. Turbulent flow is modeled by using the SST k-ω model. Numerical results show that the presence of swirling velocities in the flow field significantly affects the thrust vectoring efficiency of the nozzle. From numerical simulations of the aircraft, it was found that the aerodynamic characteristics are strongly affected by the exit air jet angle.
Coanda effect is the adhesion of fluid on a convex surface. This paper presents the effect of tem... more Coanda effect is the adhesion of fluid on a convex surface. This paper presents the effect of temperature on the Coanda flow and shows how the temperature of the surface can influence the flow behaviour. It has been found that there are two mechanisms which influence the flow behaviour; both have contrary effect on the flow. One is based on variable Prandtl number and another is based on constant Prandtl number (thermal diffusivity) effect. The increment of the thermal diffusivity has prolonged separation of the boundary layer, while other mechanism triggers the earlier detachment of the flow from the curved surface. The preliminary CFD evaluation has provided the important controlling parameter for the thrust deflection.
The energy balance for an atmospheric layer near the soil is evaluated. By integrating it over th... more The energy balance for an atmospheric layer near the soil is evaluated. By integrating it over the whole day period, a linear relationship between the global daily solar radiation on a horizontal surface and the product of the sunshine hours at clear sky with the daily maximum temperature variation is achieved. The results for the monthly averaged daily values show a comparable accuracy with some well recognized models such as the Å ngströ m-Prescott one, at least for Mediterranean climatic area. Validation of the results has been performed using old data sets which are almost contemporary and relative to the same sites with the ones used for the comparison.
The energy balance for an atmospheric layer near the soil is evaluated. By integrating it over th... more The energy balance for an atmospheric layer near the soil is evaluated. By integrating it over the whole day period a linear relationship between the global daily solar radiation incident on a horizontal surface and the product of the sunshine hours at clear sky with the maximum temperature variation in the day is achieved. The results show a comparable accuracy with some well recognized solar energy models such as the Ångström-Prescott one, at least for Mediterranean climatic area. Validation of the result has been performed using old dataset which are almost contemporary and relative to the same sites with the ones used for comparison.
This paper compares hydrogen production by photovoltaic powered electrolysis of water at sea leve... more This paper compares hydrogen production by photovoltaic powered electrolysis of water at sea level and at low stratospheric altitudes up to 21 km. All the hydrogen production process has been considered from catchable solar radiation to storage technologies. The evaluation has been performed for 1 m 2 of flat horizontal plane. It has been considered the electric energy amount produced considering variations in equilibrium temperature and in solar. Hydrogen production through electrolysis has been evaluated too.
ABSTRACT This paper aims at defining a design methodology for the global thermodynamic performanc... more ABSTRACT This paper aims at defining a design methodology for the global thermodynamic performance of a high altitude airship cabin. This design method applies to different systems, which could not use the traditional air conditioning plant layout based on bleed air intake from the compressor stage of jet engines. In the case of electrically propelled green vehicles and airships, other energy sources must be exploited. The MAAT EU FP7 project presents an innovative, energetically self sufficient, airship system based on cruiser-feeder architecture. Both the cruiser and feeder are fed by photovoltaic energy. The energy storage system by electrolysis and fuel cells with intermediate energy storage by hydrogen and oxygen is characterized by high temperature energy dispersions (about 800-1000 °C for High temperature SOFC cells). This situation encourages the definition of a novel pressurization and air conditioning system. A preliminary cabin sizing with some structural considerations, an energetic evaluation of the thermal insulation of the cabin and a general balance of the energy production system are provided
Coanda effect (adhesion of jet flow over curved surface) is fundamental characteristics of jet fl... more Coanda effect (adhesion of jet flow over curved surface) is fundamental characteristics of jet flow. In the present paper, we carried out numerical simulations to investigate Coanda flow over a curved surface and its application in a newly proposed Propulsive system "A.C.H.E.O.N" (Aerial Coanda High Efficiency Orienting jet Nozzle) which supports thrust vectoring. The ACHEON system is presently being proposed for propelling a new V/STOL airplane in European Union. This system is based on cumulative effects of three physical effects such as (1) High speed jet mixing speeds (2) Coanda effect control by electrostatic fields (3) Coanda effect adhesion of an high speed jet to a convex surface. The performance of this nozzle can be enhanced by increasing the jet deflection angle of synthetic jet over the Coanda surface. This newly proposed nozzle has wide range of applications. It can be used in industrial sector such as plasma spray gun and for direct injection in combustion chamber to enhance the efficiency of the combustion chamber. Also, we studied the effect of Dielectric barrier discharge (DBD) plasma actuators on A.C.H.E.O.N system. Dielectric barrier discharge (DBD) plasma actuators are active control devices for controlling boundary layer and to delay the flow separation over any convex surfaces. Computations were performed under subsonic condition. Two dimensional CFD calculations were carried out using Reynolds averaged Navier stokes equations (RANS). A numerical method based on finite volume formulation (FVM) was used. SST k-ω model was considered to model turbulent flow inside nozzle. DBD model was used to model the plasma. Moreover, a body force treatment was devised to model the effect of plasma and its coupling with the fluid. This preliminary result shows that, the presence of plasma near Coanda surface accelerates the flow and delays the separation and enhances the efficiency of the nozzle.
ABSTRACT Export Date: 7 December 2013, Source: Scopus, References: Pedro, G., Suleman, A., Djilal... more ABSTRACT Export Date: 7 December 2013, Source: Scopus, References: Pedro, G., Suleman, A., Djilali, N., A numerical study of the propulsive efficiency of a flapping hydrofoil (2003) International Journal for Numerical Methods in Fluids, 42, pp. 493-526;
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Papers by antonio dumas
The architecture of this airplane, which has operated actively for more than 20 years, is very interesting analyzing the implementation of a new propulsion system because of the unusual incorporation of two engines, as well as the two main landing gear shock struts of the faired main landing gear attached to short pylons on either side of the forward fuselage. This unconventional design allows an easy implementation of different propulsion units, such as the history of different experimental versions allowed.
This paper presents the preliminary definition of an increased performance cogeneration system for optimizing the energy efficiency and maximizing the thrust of ducted fan propeller. It then produces an effective design of the ACHEON nozzle for such an aircraft, the definition of the optimal positioning for stability and efficiency. In conclusion, it analyses the expected performances of the resulting aircraft architecture.
Outstanding results allows verifying an effective possibility of implementing the ACHEON Coanda effect thrust and vector propulsion system on real aircraft.
The architecture of this airplane, which has operated actively for more than 20 years, is very interesting analyzing the implementation of a new propulsion system because of the unusual incorporation of two engines, as well as the two main landing gear shock struts of the faired main landing gear attached to short pylons on either side of the forward fuselage. This unconventional design allows an easy implementation of different propulsion units, such as the history of different experimental versions allowed.
This paper presents the preliminary definition of an increased performance cogeneration system for optimizing the energy efficiency and maximizing the thrust of ducted fan propeller. It then produces an effective design of the ACHEON nozzle for such an aircraft, the definition of the optimal positioning for stability and efficiency. In conclusion, it analyses the expected performances of the resulting aircraft architecture.
Outstanding results allows verifying an effective possibility of implementing the ACHEON Coanda effect thrust and vector propulsion system on real aircraft.